1. Field of the Invention
This invention relates to a magnetic sheet recording and reproducing apparatus, and more particularly to a magnetic sheet recording and reproducing apparatus with a surface treating means for removing from the surface of the magnetic sheet dust particles, scratches and the like which would cause drop-out of the reproduction output level.
2. Description of the Prior Art
Recently, magnetic recording sheets (hereinafter referred to simply as "magnetic sheets") have come into use for various purposes. The magnetic sheet comprises a support film base with a thickness of about 3.mu. to 1 mm and a magnetic layer carried thereon with a thickness of about 0.05.mu. to 100.mu.. The magnetic sheet generally has a circular configuration with a diameter of 10 to 50 cm having a center opening for engagement with a rotating member of a magnetic sheet recording and reproducing apparatus (hereinafter referred to simply as "magnetic sheet recorder"). The magnetic layer is applied to the support film base in the form of a coating including magnetic particles and a binder. If desired, a protective layer may be provided on the magnetic layer.
As the support film base, may be used for example, polyester, polyolefin, cellulose derivertives, vinyl resins, non-magnetic metals such as copper, ceramics or laminated paper.
Generally, .gamma.-Fe.sub.2 O.sub.3, or sometimes Fe.sub.3 O.sub.4, is used as the magnetic particles. Thermoplastic resins, thermosetting resins or the like are used as the binder.
As is well known in the art, when the surface of the magnetic layer of the magnetic sheet is not flat, or when there are scratches or irregularities in the surface of the magnetic layer, drop-out of the reproduction output level is caused, i.e., the reproduction output level is suddenly lowered momentarily. Dust particles entrapped in the magnetic layer when said coating is solidified or dust particles simply adhering to the surface of the magnetic layer also cause drop-out.
There have been proposed various methods for removing dust particles adhering to the surface of a magnetic sheet. In one of the methods, dust particles are removed by means of a brush. In another method, there is used a cleaning sheet formed of a material such as a non-woven fabric or the like having a soft and rough surface or a porous surface. However, such conventionally proposed methods are only directed to removing dust particles simply adhering to the surface of the magnetic layer, and can remove neither irregularities in the surface of the magnetic layer nor dust particles entrapped in the magnetic layer.